How to update existing column values in data.table?

Question

I just started this programming, apologize for asking this simple question but I am stuck. I have a data.table called s3: s3: ``` ClaimID dx dxgroup 15nhbfcgcda 113.8 NA 15nhbfcgcda 156.8 NA 15nhbfcgcda 110.8 059 15nhbfcfssa 135.8 NA 15nhb4dfgda V70.3 NA 15nhbf644da 118.8 042 ``` S3 has 30000 rows. I want to apply this logic: ``` If dxgroup = NA( If dx (fisrt 4 characters match with)= (2024, 2967, 9786,9788,8263) then dxgroup = (first 4 character of dx) else dx (fisrt 3 characters match with) = (V70, 042,897) then dxgroup = (first 3 character of dx) else dxgroup = dx ) ``` Result should be like : ``` ClaimID dx dxgroup 15nhbfcgcda 113.8 113.8 15nhbfcgcda 156.8 156.8 15nhbfcgcda 110.8 059 15nhbfcfssa 135.8 135.8 15nhb4dfgda V70.3 V70 15nhbf644da 118.8 042 ``` Please advice ? I apologize: It is my first time I am asking something here, so not used to yet. So I did something like this(I have no if this is correct and I got error as well): sample4<-sample3[, dxgroup := { if (dxgroup == NA…

Accepted Answer

You have the logic all set.

Note that with data.table (well, almost all of `R`), you can wrap the `j` in `{curly brackets}` and the final statement in the brackets is what will be assigned. eg:

```
DT[,  dxgroup :=  { if (clause1)  
                     {if (foo) beebar else bar}
                  else chewybar
                  } 
  ]
```

How to update existing column values in data.table?

Solution

Problem